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Publication Record


Arachidonic Acid Kills Staphylococcus aureus through a Lipid Peroxidation Mechanism.
Beavers WN, Monteith AJ, Amarnath V, Mernaugh RL, Roberts LJ, Chazin WJ, Davies SS, Skaar EP
(2019) mBio 10:
MeSH Terms: Animals, Anti-Bacterial Agents, Arachidonic Acid, Brain, Dose-Response Relationship, Drug, Drug Resistance, Bacterial, Female, Kidney, Lipid Peroxidation, Lipids, Mice, Mice, Inbred BALB C, Microbial Sensitivity Tests, Mutation, Neutrophils, Oxidative Stress, Reactive Oxygen Species, Spleen, Staphylococcal Infections, Staphylococcus aureus, Teichoic Acids
Show Abstract · Added March 11, 2020
infects every niche of the human host. In response to microbial infection, vertebrates have an arsenal of antimicrobial compounds that inhibit bacterial growth or kill bacterial cells. One class of antimicrobial compounds consists of polyunsaturated fatty acids, which are highly abundant in eukaryotes and encountered by at the host-pathogen interface. Arachidonic acid (AA) is one of the most abundant polyunsaturated fatty acids in vertebrates and is released in large amounts during the oxidative burst. Most of the released AA is converted to bioactive signaling molecules, but, independently of its role in inflammatory signaling, AA is toxic to Here, we report that AA kills through a lipid peroxidation mechanism whereby AA is oxidized to reactive electrophiles that modify macromolecules, eliciting toxicity. This process is rescued by cotreatment with antioxidants as well as in a strain genetically inactivated for (USA300 mutant) that produces lower levels of reactive oxygen species. However, resistance to AA stress in the USA300 mutant comes at a cost, making the mutant more susceptible to β-lactam antibiotics and attenuated for pathogenesis in a murine infection model compared to the parental methicillin-resistant (MRSA) strain, indicating that resistance to AA toxicity increases susceptibility to other stressors encountered during infection. This report defines the mechanism by which AA is toxic to and identifies lipid peroxidation as a pathway that can be modulated for the development of future therapeutics to treat infections. Despite the ability of the human immune system to generate a plethora of molecules to control infections, is among the pathogens with the greatest impact on human health. One class of host molecules toxic to consists of polyunsaturated fatty acids. Here, we investigated the antibacterial properties of arachidonic acid, one of the most abundant polyunsaturated fatty acids in humans, and discovered that the mechanism of toxicity against proceeds through lipid peroxidation. A better understanding of the molecular mechanisms by which the immune system kills , and by which avoids host killing, will enable the optimal design of therapeutics that complement the ability of the vertebrate immune response to eliminate infections.
Copyright © 2019 Beavers et al.
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21 MeSH Terms
Helicobacter pylori antimicrobial resistance and antibiotic consumption in the low-resource Central America setting.
Ortiz V, Estevez-Ordonez D, Montalvan-Sanchez E, Urrutia-Argueta S, Israel D, Krishna US, Romero-Gallo J, Wilson KT, Peek RM, Dominguez R, Morgan DR
(2019) Helicobacter 24: e12595
MeSH Terms: Adult, Aged, Amoxicillin, Anti-Bacterial Agents, Central America, Drug Resistance, Bacterial, Female, Helicobacter Infections, Helicobacter pylori, Humans, Levofloxacin, Male, Microbial Sensitivity Tests, Middle Aged
Show Abstract · Added May 23, 2019
BACKGROUND - Antimicrobial resistance is a global public health problem, particularly in low- and middle-income countries (LMICs), where antibiotics are often obtained without a prescription. H. pylori antimicrobial resistance patterns are informative for patient care and gastric cancer prevention programs, have been shown to correlate with general antimicrobial consumption, and may guide antimicrobial stewardship programs in LMICs. We report H. pylori resistance and antimicrobial utilization patterns for western Honduras, representative of rural Central America.
METHODS - In the context of the western Honduras gastric cancer epidemiology initiative, gastric biopsies from 189 patients were studied for culture and resistance patterns. Antimicrobial utilization was investigated for common H. pylori treatment regimens from regional public (7 antimicrobials) and national private (4 antimicrobials) data, analyzed in accordance with WHO anatomical therapeutic chemical defined daily doses (DDD) method and expressed as DDD/1000 inhabitants per day (DID) and per year (DIY).
RESULTS - H. pylori was successfully cultured from 116 patients (56% males, mean age: 54), and nearly all strains were cagA+ and vacAs1m1+ positive (99% and 90.4%, respectively). Unexpectedly, high resistance was noted for levofloxacin (20.9%) and amoxicillin (10.7%), while metronidazole (67.9%) and clarithromycin (11.2%) were similar to data from Latin America. Significant associations with age, gender, or histology were not noted, with the exception of levofloxacin (28%, P = 0.01) in those with histology limited to non-atrophic gastritis. Total antimicrobial usage in western Honduras of amoxicillin (17.3 DID) and the quinolones had the highest relative utilizations compared with other representative nations.
CONCLUSIONS - We observed significant H. pylori resistance to amoxicillin and levofloxacin in the context of high community antimicrobial utilization. This has implications in Central America for H. pylori treatment guidelines as well as antimicrobial stewardship programs.
© 2019 John Wiley & Sons Ltd.
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14 MeSH Terms
An Acinetobacter baumannii, Zinc-Regulated Peptidase Maintains Cell Wall Integrity during Immune-Mediated Nutrient Sequestration.
Lonergan ZR, Nairn BL, Wang J, Hsu YP, Hesse LE, Beavers WN, Chazin WJ, Trinidad JC, VanNieuwenhze MS, Giedroc DP, Skaar EP
(2019) Cell Rep 26: 2009-2018.e6
MeSH Terms: Acinetobacter baumannii, Animals, Anti-Bacterial Agents, Bacterial Proteins, Cell Wall, Drug Resistance, Bacterial, Male, Metalloendopeptidases, Mice, Mice, Inbred C57BL, Pneumonia, Bacterial, Zinc
Show Abstract · Added March 26, 2019
Acinetobacter baumannii is an important nosocomial pathogen capable of causing wound infections, pneumonia, and bacteremia. During infection, A. baumannii must acquire Zn to survive and colonize the host. Vertebrates have evolved mechanisms to sequester Zn from invading pathogens by a process termed nutritional immunity. One of the most upregulated genes during Zn starvation encodes a putative cell wall-modifying enzyme which we named ZrlA. We found that inactivation of zrlA diminished growth of A. baumannii during Zn starvation. Additionally, this mutant strain displays increased cell envelope permeability, decreased membrane barrier function, and aberrant peptidoglycan muropeptide abundances. This altered envelope increases antibiotic efficacy both in vitro and in an animal model of A. baumannii pneumonia. These results establish ZrlA as a crucial link between nutrient metal uptake and cell envelope homeostasis during A. baumannii pathogenesis, which could be targeted for therapeutic development.
Copyright © 2019 Vanderbilt University Medical Center. Published by Elsevier Inc. All rights reserved.
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12 MeSH Terms
Toxicity and repair of DNA adducts produced by the natural product yatakemycin.
Mullins EA, Shi R, Eichman BF
(2017) Nat Chem Biol 13: 1002-1008
MeSH Terms: Biological Products, DNA Adducts, DNA Damage, DNA Repair, Drug Resistance, Bacterial, Duocarmycins, Indoles, Molecular Structure, Pyrroles
Show Abstract · Added August 26, 2019
Yatakemycin (YTM) is an extraordinarily toxic DNA alkylating agent with potent antimicrobial and antitumor properties and is the most recent addition to the CC-1065 and duocarmycin family of natural products. Though bulky DNA lesions the size of those produced by YTM are normally removed from the genome by the nucleotide-excision repair (NER) pathway, YTM adducts are also a substrate for the bacterial DNA glycosylases AlkD and YtkR2, unexpectedly implicating base-excision repair (BER) in their elimination. The reason for the extreme toxicity of these lesions and the molecular basis for the way they are eliminated by BER have been unclear. Here, we describe the structural and biochemical properties of YTM adducts that are responsible for their toxicity, and define the mechanism by which they are excised by AlkD. These findings delineate an alternative strategy for repair of bulky DNA damage and establish the cellular utility of this pathway relative to that of NER.
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9 MeSH Terms
Isoniazid-monoresistant tuberculosis is associated with poor treatment outcomes in Durban, South Africa.
van der Heijden YF, Karim F, Mufamadi G, Zako L, Chinappa T, Shepherd BE, Maruri F, Moosa MS, Sterling TR, Pym AS
(2017) Int J Tuberc Lung Dis 21: 670-676
MeSH Terms: Adult, Antitubercular Agents, Drug Resistance, Bacterial, Female, HIV Infections, Humans, Isoniazid, Logistic Models, Longitudinal Studies, Male, Microbial Sensitivity Tests, Mycobacterium tuberculosis, Retrospective Studies, South Africa, Treatment Failure, Treatment Outcome, Tuberculosis
Show Abstract · Added March 14, 2018
SETTING - A large tuberculosis (TB) clinic in Durban, South Africa.
OBJECTIVE - To determine the association between isoniazid (INH) monoresistant TB and treatment outcomes.
DESIGN - We performed a retrospective longitudinal study of patients seen from 2000 to 2012 to compare episodes of INH-monoresistant TB with those of drug-susceptible TB using logistic regression with robust standard errors. INH-monoresistant TB was treated with modified regimens.
RESULTS - Among 18 058 TB patients, there were 19 979 TB episodes for which drug susceptibility testing was performed. Of these, 557 were INH-monoresistant and 16 311 were drug-susceptible. Loss to follow-up, transfer, and human immunodeficiency virus (HIV) co-infection (41% had known HIV status) were similar between groups. INH-monoresistant episodes were more likely to result in treatment failure (4.1% vs. 0.6%, P < 0.001) and death (3.2% vs. 1.8%, P = 0.01) than drug-susceptible episodes. After adjustment for age, sex, race, retreatment status, and disease site, INH-monoresistant episodes were more likely to have resulted in treatment failure (OR 6.84, 95%CI 4.29-10.89, P < 0.001) and death (OR 1.81, 95%CI 1.11-2.95, P = 0.02).
CONCLUSION - INH monoresistance was associated with worse clinical outcomes than drug-susceptible TB. Our findings support the need for rapid diagnostic tests for INH resistance and improved treatment regimens for INH-monoresistant TB.
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17 MeSH Terms
Colonization resistance: The deconvolution of a complex trait.
Olsan EE, Byndloss MX, Faber F, Rivera-Chávez F, Tsolis RM, Bäumler AJ
(2017) J Biol Chem 292: 8577-8581
MeSH Terms: Animals, Anti-Bacterial Agents, Bacteria, Bacterial Infections, Drug Resistance, Bacterial, Gastrointestinal Microbiome, Humans, Intestines
Show Abstract · Added March 30, 2020
Carbapenemase-producing Enterobacteriaceae are an emerging threat to hospitals worldwide, and antibiotic exposure is a risk factor for developing fecal carriage that may lead to nosocomial infection. Here, we review how antibiotics reduce colonization resistance against Enterobacteriaceae to pinpoint possible control points for curbing their spread. Recent work identifies host-derived respiratory electron acceptors as a critical resource driving a post-antibiotic expansion of Enterobacteriaceae within the large bowel. By providing a conceptual framework for colonization resistance against Enterobacteriaceae, these mechanistic insights point to the metabolism of epithelial cells as a possible target for intervention strategies.
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
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MeSH Terms
Bacterial Density, Serotype Distribution and Antibiotic Resistance of Pneumococcal Strains from the Nasopharynx of Peruvian Children Before and After Pneumococcal Conjugate Vaccine 7.
Hanke CR, Grijalva CG, Chochua S, Pletz MW, Hornberg C, Edwards KM, Griffin MR, Verastegui H, Gil AI, Lanata CF, Klugman KP, Vidal JE
(2016) Pediatr Infect Dis J 35: 432-9
MeSH Terms: Anti-Bacterial Agents, Bacterial Load, Child, Preschool, Cross-Sectional Studies, Drug Resistance, Bacterial, Female, Heptavalent Pneumococcal Conjugate Vaccine, Humans, Infant, Male, Microbial Sensitivity Tests, Nasopharynx, Peru, Pneumococcal Infections, Prevalence, Serogroup, Streptococcus pneumoniae
Show Abstract · Added July 27, 2018
BACKGROUND - Pneumococcal conjugate vaccines (PCV) have decreased nasopharyngeal carriage of vaccine types but little data exist from rural areas. We investigated bacterial density, serotype distribution and antibiotic resistance of pneumococcal strains within the nasopharynx of young children in the Peruvian Andes, 2 years after PCV7 was introduced.
METHODS - Pneumococcal strains were isolated from a subset of 125 children from our Peruvian cohort, who entered the study in 2009 and had pneumococcus detected in the nasopharynx in both 2009 and during follow-up in 2011. Strains were Quellung serotyped and tested for susceptibility to antibiotics. Bacterial density was determined by quantitative polymerase chain reaction.
RESULTS - The prevalence of PCV7 strains decreased from 48% in 2009 to 28.8% in 2011, whereas non-PCV7 types increased from 52% to 71.2% (P = 0.002). There was a 3.5-fold increase in carriage of serotype 6C in 2011 (P = 0.026). Vaccination with PCV7 did not affect pneumococcal density in children colonized by a PCV7 type but did increase density in those colonized with a non-PCV7 type. Antibiotic resistance did not change after vaccine introduction; strains were nonsusceptible to tetracycline (97.2%), trimethoprim-sulfamethoxazole (56.4%), penicillin (34%), erythromycin (22.4%), chloramphenicol (18.8%) and clindamycin (12.4%).
CONCLUSIONS - Serotype replacement was observed post-PCV7 vaccination with a concomitant, not previously recognized, increased nasopharyngeal density.
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MeSH Terms
Helicobacter pylori Resists the Antimicrobial Activity of Calprotectin via Lipid A Modification and Associated Biofilm Formation.
Gaddy JA, Radin JN, Cullen TW, Chazin WJ, Skaar EP, Trent MS, Algood HM
(2015) mBio 6: e01349-15
MeSH Terms: Acyltransferases, Anti-Bacterial Agents, Bacterial Proteins, Biofilms, Cell Membrane, Drug Resistance, Bacterial, Helicobacter pylori, Hydrophobic and Hydrophilic Interactions, Leukocyte L1 Antigen Complex, Lipid A, Lipopolysaccharides, Phenotype
Show Abstract · Added February 5, 2016
UNLABELLED - Helicobacter pylori is one of several pathogens that persist within the host despite a robust immune response. H. pylori elicits a proinflammatory response from host epithelia, resulting in the recruitment of immune cells which manifests as gastritis. Relatively little is known about how H. pylori survives antimicrobials, including calprotectin (CP), which is present during the inflammatory response. The data presented here suggest that one way H. pylori survives the nutrient sequestration by CP is through alteration of its outer membrane. CP-treated H. pylori demonstrates increased bacterial fitness in response to further coculture with CP. Moreover, CP-treated H. pylori cultures form biofilms and demonstrate decreased cell surface hydrophobicity. In response to CP, the H. pylori Lpx lipid A biosynthetic enzymes are not fully functional. The lipid A molecules observed in H. pylori cultures treated with CP indicate that the LpxF, LpxL, and LpxR enzyme functions are perturbed. Transcriptional analysis of lpxF, lpxL, and lpxR indicates that metal restriction by CP does not control this pathway through transcriptional regulation. Analyses of H. pylori lpx mutants reveal that loss of LpxF and LpxL results in increased fitness, similar to what is observed in the presence of CP; moreover, these mutants have significantly increased biofilm formation and reduced cell surface hydrophobicity. Taken together, these results demonstrate a novel mechanism of H. pylori resistance to the antimicrobial activity of CP via lipid A modification strategies and resulting biofilm formation.
IMPORTANCE - Helicobacter pylori evades recognition of the host's immune system by modifying the lipid A component of lipopolysaccharide. These results demonstrate for the first time that the lipid A modification pathway is influenced by the host's nutritional immune response. H. pylori's exposure to the host Mn- and Zn-binding protein calprotectin perturbs the function of 3 enzymes involved in the lipid A modification pathway. Moreover, CP treatment of H. pylori, or mutants with an altered lipid A, exhibit increased bacterial fitness and increased biofilm formation. This suggests that H. pylori modifies its cell surface structure to survive under the stress imposed by the host immune response. These results provide new insights into the molecular mechanisms that influence the biofilm lifestyle and how endotoxin modification, which renders H. pylori resistant to cationic antimicrobial peptides, can be inactivated in response to sequestration of nutrient metals.
Copyright © 2015 Gaddy et al.
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12 MeSH Terms
Comparison of clinical prediction models for resistant bacteria in community-onset pneumonia.
Self WH, Wunderink RG, Williams DJ, Barrett TW, Baughman AH, Grijalva CG
(2015) Acad Emerg Med 22: 730-40
MeSH Terms: Adult, Aged, Algorithms, Anti-Bacterial Agents, Community-Acquired Infections, Drug Resistance, Bacterial, Emergency Service, Hospital, Female, Humans, Male, Middle Aged, Pneumonia, Bacterial, ROC Curve, Retrospective Studies, Risk Assessment
Show Abstract · Added July 27, 2018
OBJECTIVES - Six recently published algorithms classify pneumonia patients presenting from the community into high- and low-risk groups for resistant bacteria. Our objective was to compare performance of these algorithms for identifying patients infected with bacteria resistant to traditional community-acquired pneumonia antibiotics.
METHODS - This was a retrospective study of consecutive adult patients diagnosed with pneumonia in an emergency department and subsequently hospitalized. Each patient was classified as high or low risk for resistant bacteria according to the following algorithms: original health care-associated pneumonia (HCAP) criteria, Summit criteria, Brito and Niederman strategy, Shorr model, Aliberti model, and Shindo model. The reference for comparison was detection of resistant bacteria, defined as methicillin-resistant Staphylococcus aureus or Gram-negative bacteria resistant to ceftriaxone or levofloxacin.
RESULTS - A total of 614 patients were studied, including 36 (5.9%) with resistant bacteria. The HCAP criteria classified 304 (49.5%) patients as high risk, with an area under the receiver operating characteristic curve (AUC) of 0.63 (95% confidence interval [CI] = 0.54 to 0.72), sensitivity of 0.69 (95% CI = 0.52 to 0.83), and specificity of 0.52 (95% CI = 0.48 to 0.56). None of the other algorithms improved both sensitivity and specificity or significantly improved the AUC. Compared to the HCAP criteria, the Shorr and Aliberti models classified more patients as high risk, resulting in higher sensitivity and lower specificity. The Shindo model classified fewer patients as high risk, with lower sensitivity and higher specificity.
CONCLUSIONS - All algorithms for identification of resistant bacteria included in this study had suboptimal performance to guide antibiotic selection. New strategies for selecting empirical antibiotics for community-onset pneumonia are necessary.
© 2015 by the Society for Academic Emergency Medicine.
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MeSH Terms
A comparison of interview methods to ascertain fluoroquinolone exposure before tuberculosis diagnosis.
Van Der Heijden YF, Maruri F, Holt E, Mitchel E, Warkentin J, Sterling TR
(2015) Epidemiol Infect 143: 960-5
MeSH Terms: Adult, Anti-Bacterial Agents, Databases, Factual, Delayed Diagnosis, Drug Resistance, Bacterial, Female, Fluoroquinolones, Humans, Interviews as Topic, Male, Medical History Taking, Medical Records, Middle Aged, Pharmacies, Surveys and Questionnaires, Tennessee, Tuberculosis, Tuberculosis, Pulmonary
Show Abstract · Added February 17, 2016
SUMMARY Fluoroquinolone use before tuberculosis (TB) diagnosis delays the time to diagnosis and treatment, and increases the risk of fluoroquinolone-resistant TB and death. Ascertainment of fluoroquinolone exposure could identify such high-risk patients. We compared four methods of ascertaining fluoroquinolone exposure in the 6 months prior to TB diagnosis in culture-confirmed TB patients in Tennessee from January 2007 to December 2009. The four methods included a simple questionnaire administered to all TB suspects by health department personnel (FQ-Form), an in-home interview conducted by research staff, outpatient and inpatient medical record review, and TennCare pharmacy database review. Of 177 TB patients included, 72 (41%) received fluoroquinolones during the 6 months before TB diagnosis. Fluoroquinolone exposure determined by review of inpatient and outpatient medical records was considered the gold standard for comparison. The FQ-Form had 61% [95% confidence interval (CI) 48-73] sensitivity and 93% (95% CI 85-98) specificity (agreement 79%, kappa = 0.56) while the in-home interview had 28% (95% CI 18-40) sensitivity and 99% (94-100%) specificity (agreement 68%, kappa = 0.29). A simple questionnaire administered by health department personnel identified fluoroquinolone exposure before TB diagnosis with moderate reliability.
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18 MeSH Terms